1. Field of the Invention
This invention relates to the recovery of monobutyltin trichloride (hereinafter also referred to as “MBTC”) from the effluent stream of a chemical vapor deposition (hereinafter also referred to as “CVD”) coating process practiced to apply a tin oxide film to a substrate, and more particularly, to the recovery of MBTC and methyl isobutyl ketone (hereinafter also referred to as “MIBK”) from the effluent stream of a CVD coating process practiced to apply a fluorine doped tin oxide film to a glass ribbon, and to introduce the recovered MBTC and MIBK to the CVD coating process, or any similar CVD coating process.
2. Discussion of the Present Technology
Environmental coatings are applied to glass sheets to selectively control the transmission of ultraviolet radiation, visible light, and infrared energy, e.g. fluorine doped tin oxide is applied by the chemical vapor deposition coating process to a glass ribbon to reflect infrared energy. The coating is of commercial interest because it reflects infrared energy to reduce the heating costs during the winter months and to reduce the load on the air conditioners during the summer months. In addition to reflecting infrared energy, the tin oxide doped with fluorine is electrically conductive making it useful in the manufacture of photovoltaic cells and electrically heated glass used for anti-fog commercial refrigerator doors, and heating systems for removing fog and ice from aircraft transparencies.
Although the presently available CVD coating processes for applying tin oxide are commercially acceptable, there are limitations. More particularly, the CVD coating processes usually include vaporizing coating precursors including MBTC, MIBK and water (hereinafter also referred to as “H2O”) to deposit a tin oxide film, and the addition of trifluoroacetic acid (hereinafter also referred to as “TFA”) to deposit fluorine doped tin oxide film. As is appreciated by those skilled in the art, the MIBK, among other things, stabilizes the coating solution and increases the solubility of the TFA in MBTC. The efficiency of the CVD coating process for depositing the tin oxide film is less than 15% resulting in more than 85% of the MBTC in the coating precursors present in the effluent vapor stream of the coating process.
Exhaust channels are provided adjacent the coating zone or coating area to remove the effluent stream of vapor. As discussed below in more detail, a portion of the effluent stream of vapor is condensed, and a portion of the effluent stream of vapor is solidified and captured in a baghouse. The usual practice is to incinerate the condensate and to bury the solid waste products in accordance to federal, state and local environmental regulations.
As can be appreciated, by those skilled in the art, at the present time, MBTC is the most expensive component of the coating precursors. It would be advantageous, therefore, to provide a system and/or to practice a method at the coating facility, or at a chemical recovery facility to reclaim most, if not all, of the MBTC from the effluent coating vapors and to introduce the recovered MBTC back into the coating process.